A lot of times, double amping is really no big deal. I mean, it's a lot easier for an amp to drive a line input (thousands of ohms impedance, thus low current and so on) than it is for that amp to drive some actual headphones.
And DX I think is like D1, which has ~100 ohms output impedance. It's supposed to be a normal line output that's driven by some high-quality audio op amp that's not particularly some high-current output part. It's not really much of an amp in the sense that most people are talking about.
i did state that i didnt know anything about pc soundcards, and i also said that noise may be added, not that it definitely would. its just the my laptops headphone jack is really really hissy, which was one of the reasons i got an external dac/amp in the first place. so if i were to send a signal through it and into my O2 id get sound thats just as bad. this is what i was talking about.
entirely unrelated edit: my mouses scroll wheel stopped working about a week ago and i was all upset about getting a new one because i really like my mouse... then my roomate walked in and asked to use my printer. i obliged and when getting up to fetch a glass of water i accidentally dropped the mouse on the floor. now its working fine again! im so pleased!
Edited by adamlr - 5/12/13 at 8:52am